Check valve and a seal for a check valve

ABSTRACT

A horizontal check valve has a swinging clapper (16) eccentric with a tapered valve seat (14) and carrying a floating ring seal. There is clearance between the clapper (16) and the passage wall at the bottom so that reverse flow urges the ring seal into the taper. The clapper (16) abuts an abutment surface (15) formed by the valve body (10) around the valve seat so that the hydrostatic forces exerted on the clapper (16) by the reverse fluid flow are reacted by the abutment surface and not by the tapered seat (14).

DESCRIPTION

This invention relates to check valves.

A check valve comprises a housing which forms a through passage which isto be connected into a fluid pipeline when the valve is in use. There isan annular valve seat which extends around the passage, and anobturating member which is cooperable with the valve seat to close thethrough passage and which is displaceable from the valve seat to allowfluid flow through the through passage.

U.S. Pat. No. 4,410,007 discloses a check valve comprising a housingwhich forms a through passage which is to be connected into a fluidpipeline when the valve is in use, the housing including an annularvalve seat which extends around the passage and tapers towards theupstream end of the passage in the context of the normal direction offlow through the passage, and an obturating member cooperable with thevalve seat to close the through passage and displaceable from the valveseat to allow fluid flow through the through passage, the obturatingmember carrying an annular seal which effects a metal to metal sealbetween the obturating member and the valve seat when the throughpassage is closed by the obturating member. In the context that it isdifficult to make such metal to metal seals leak proof, a soft sealbackup to the main metal to metal seal is provided and provision is madefor reverse fluid flow to be conducted through the obturating member andapplied to the soft seal so as to expand it into engagement with thevalve seat to form a secondary seal so that flow through the check valveis prevented.

One aspect of this invention arises from our appreciation that thesealing forces that act between the annular seal and the valve seatwould be increased if the angle of taper of the valve seat is reduced ascompared with that of the tapered valve seat that is incorporated in thecheck valve disclosed in U.S. Pat. No. 4,410,007, and that the risk ofjamming of the obturating member in the resultant tapered orifice couldbe avoided by arranging for the obturating member to make direct face toface contact with an abutment surface separate from the tapered surfaceof the valve seat so that the hydrostatic forces applied to theobturating member by the reverse fluid flow would be reacted by theabutment surface and not be the tapered surface of the valve seat.

Known forms of sub-sea check valve are either provided with aremotely-controllable actuator having an actuating element which ispermanently coupled to the obturating member, the actuator beingoperable to positively seat the obturating member and to unseat it asrequired, or are arranged with the obturating member mounted for freepivotal movement within the housing such that it floats in normal fluidflow through the through passage in one direction and is therebydisplaced from the valve seat, but is caused to seat on the valve seatby a tendency for fluid to flow through the through passage in theopposite direction whereby to close the through passage and inhibit suchflow in that opposite direction. The former variety of sub-sea checkvalve has the advantage that the obturating member can be displaced fromthe through passage into an alcove in the housing by operation of theactuator so as to leave the through passage clear for passage through itof a device known as a pig which is for effecting any one of a number offunctions such as cleaning the walls of the passage, removal of debrisor measuring the inside diameter of the passage, but it does not closeautomatically in response to certain conditions, say any tendency forthe direction of flow to reverse such as would occur in the event of afailure in the pipeline upstream of the check valve. The latter varietywill close automatically but suffers from the disadvantages that atleast part of the obturating member obstructs the path of a pig since iteither floats in fluid flow through the pipe or seats on the valve seatdue to the action of gravity.

Another object of this invention is to provide an improved from of checkvalve which is suitable for use as a sub-sea check valve.

According to another aspect of this invention there is provided a checkvalve comprising a housing which forms a through passage which is to beconnected into a fluid pipeline when the valve is in use, an annularvalve seat which extends around the passage, an obturating membercooperable with the valve seat to close the through passage anddisplaceable from the valve seat to allow fluid flow through the throughpassage, and a remotely controllable actuator which is operable todisplace the obturating member from the through passage unobstructed,wherein an actuating element of the actuator is coupled to theobturating member by a buckling link which serves as a tie by which theobturating member is displaced into the alcove by operation of theactuator but which can buckle to allow free movement of the obturatingmember relative to the valve seat independently of the actuator when thelatter is inoperative.

The obturating member may be pivotally mounted within the housing.Conveniently the obturating member is suspended from a closure memberwhich is releasably secured to the valve body to close an aperture inthe tope of the valve body. The valve seat may be mounted removablywithin the valve body at a location relative to said aperture such thatit can be lifted from the valve body through the aperture when theclosure member has been removed.

Preferably the check valve is a check valve according to said one aspectof this invention.

Another object of this invention is to provide an improved floating ringseal. Hence, according to another aspect of this invention, there isprovided a floating ring seal comprising an annular peripheral portionwhich forms a shallow concave radially outer peripheral sealing surfacehaving a greater outside diameter at one end than at the other, whereinthe peripheral portion is formed at the radially outer edge of aradially convoluted annular portion. The radially convoluted annularportion maybe connected to the peripheral portion at said one endthereof. Conveniently the radially inner periphery of the convolutedannular portion is formed as a thickened rib.

Check valves in which this invention is embodied are described now byway of example with reference to the accompanying drawings, of which:-

FIG. 1 is a plan view of a check valve which is also a manually-operablestop or shut-off valve;

FIG. 2 is a transverse cross-section on the line II--II in FIG. 1 of thevalve shown in FIG. 1 in the check valve mode, with the clapper shownseated, the open position of the clapper being shown chain-dotted;

FIG. 3 is a sectioned fragment of the valve shown in FIG. 1, the sectionbeing on the line III--III in FIG. 1;

FIG. 4 is an enlarged view of detail A in FIG. 2;

FIG. 5 is a view similar to FIG. 4 illustrating a different floatingseal;

FIG. 6 is a transverse cross-section of a sub-sea check valve with theclapper shown seated; and

FIG. 7 is a fragmentary view, similar to a major portion of FIG. 6, butwith the clapper unseated by fluid flow in the direction indicated byarrow B in FIG. 6.

FIGS. 1 and 2 show that the check valve comprises a housing formed by avalve body 10 and a bonnet 11 which is releasably secured to the body10. A through bore 12 extends through the body 10 and forms a throughpassage for fluid flow. An aperture 13 which communicates with thethrough bore 12 is formed at the top of the valve body 10. The aperture13 is closed by the bonnet 11 so as to form an alcove which is above thethrough bore 12 and in communication with it.

An annular metal valve seat 14 is mounted in the valve body 10 so as toextend circumferentially around the through bore 12. The valve seat 14is located at the upstream end of the aperture 13 in the sense of thedirection of normal fluid flow through the through passage 12 which isindicated by the arrow B. The upper part of the valve seat 14 is seatedin a respective shoulder 14A which is formed in the valve body 10 at theupstream end of the aperture 13.

The lower part of the valve seat 14 is seated in a respective groove14B. The valve seat 14 is seated in both the shoulder 14A and the groove14B between the top and bottom around both sides of the through bore,the depths of the shoulder 14A and the groove 14B changing progressivelyaround the bore 12 such that there is a gradual transition from theshoulder 14A at the top to the groove 14B at the bottom. The valve body10 forms an abutment surface 15 at the top of, and around the remainderof the valve seat 14 that projects from the groove 14B down the sides ofthe through bore 12, the abutment surface 15 being substantially flushwith the downstream face of the valve seat 14 (and thereby substantiallynormal to the axis of the through bore 12) and being crescent-shaped.

An obturating member, in the form of a clapper 16 fixed to a lever 17,cooperates with the valve seat 14 and the surrounding abutment surface15 to close the through passage 12 when seated. The portion of theclapper 16 that is fixed to the lever 17 is a disc portion 16A which iseccentric to the valve seat 14 when the clapper 16 is seated, the centreof the disc portion 16A being displaced vertically upwards relative tothe axis of the through bore 12. The remainder of the clapper 16 is anose portion 16B which projects into the central aperture of the annularvalve seat 14 with clearance therearound when the clapper 16 is seated,the nose portion 16B and the valve seat 14 being substantiallyconcentric. Hence there is face to face contact between the disc portion16A of the clapper 16 and the annular abutment surface 15 over acrescent shaped area at the top and down the sides but not at thebottom.

The lever 17 is cranked. It is fulcrummed on a hinge pin 18 which isjournalled in a support 19. The latter is integral with the body 10. Itis located within the alcove above the annular valve seat 14 and it hasan aperture in it (see FIG. 1) through which the lever 17 projects, theaperture being shaped and sized to allow the lever 17 to swing theclapper 16 between its open and closed positions. The hinge pin 18projects from the body 10 and has a handle 20 fitted to it at its outerend. Two axially aligned pegs 18A project radially from the hinge pin18, each through a respective circumferentially extending slot 18B inthe portion of the layer 17 that surrounds the hinge pin 18. The page18A are movable from the upstanding location shown in FIG. 2, in whichthey permit swinging movement of the obturating member between the openand closed positions of the clapper 16, to a horizontal location inwhich they interact with the ends of the slots 18B to stop angularmovement of the lever 17 and hold the clapper 16 closed. Such movementof the page 18A is effected by operation of the handle 20 to rotate thehinge pin 18 in the support 19.

FIG. 4 shows the detailed construction of the annular valve seat 14 atthe bottom of the through bore 12 and of the cooperating part of theclapper 16 including a floating metal seal ring 21 which engages atapered surface 14C of the seat 14 when the clapper 16 is seated. Thetapered surface 14C tapers towards the upstream end of the through bore12.

The floating seal ring 21 has a shallow concave radially outerperipheral surface 21A, and its outside diameter is greater at itsdownstream end than at its upstream end. It has a substantially U-shapedcross-section, the annular arms 21B and 21C of the U-section seal ring21 extending radially inwardly into an annular cavity formed between theclapper disc portion 16A and a retaining nut 22 which is screwed ontothe clapper nose portion 16B.

The dimensions of the clapper disc portion 16A, the floating seal ring21 and the tapered surface 14C of the valve seat 14 are such that aninterference fit is established between the seal ring 21 and the valveseat 14 when the clapper 16 is seated.

The check valve is inserted into a pipeline in use. Normal fluid flow isfrom the left to the right of FIG. 1 and 2, as shown by arrow B. Theobturating member, comprising the clapper 16 and the lever 17, is freelypivotable relative to the rest of the structure when the handle 20 isset in its position for normal check valve operation. the pegs 18A beingupstanding as shown in FIG. 2. The clapper 16 floats in the fluid andthus is displaced from the annular valve seat 14.

Should there be a reversal of the direction of fluid flow, the clapper16 will swing down to seat with such reverse flow. Initial contact withthe seat 14 will be by engagement of one of the edges of the concaveouter surface 21A of the floating seal ring 21 with the tapered seatsurface 14C but that will be followed instantaneously by face to facecontact of the clapper disc portion 16A with the abutment surface 15 sothat shock loads due to impact, etc., and the hydrostactic loading onthe clapper 16 will be reacted directly by the body 10 and not appliedto the floating ring seal 21.

As can be seen from FIG. 4, once the clapper 16 is seated, the clearancebetween the bottom of the clapper disc portion 16A on the one hand, andthe valve seat 14 and the surface of the through bore 12 on the otherhand provides access for the reverse fluid flow to the floating ringseal 21 so that that reverse fluid flow forces the seal 21 further intothe seat taper. Travel of the seal 21 is limited by its abutment withthe clapper 16 which in turn is restricted from travel by the abutmentof its disc portion 16A with the abutment surface 15. Such reverse fluidflow will pass between the clapper disc portion 16A and the adjacentradial arm 21B of the floating seal ring 21 into the circumferentiallyextending cavity of that seal 21. Such fluid pressure in that cavitywill act to urge the other radial arm 21C into fluid tight contact withthe retaining nut 22 and also will urge the seal 21 both radiallyoutwardly and axially into fluid tight contact with the tapered seatsurface 14C. Hence fluid tight contact between the seal 21 and the valveseat 14 is established solely by the action of fluid pressure on theseal 21. It may be desirable to provide some elastomeric material in thecavity of the seal 21 in order to ensure a fluid tight seal between theseal 21 and the retaining unit 22.

The angle of taper of the tapered surface 14C should be as small as ispracticable (say 10° to the axis of the through bore 12) so as tomaximise the forces that urge the floating seat 21 into sealingengagement with the tapered surface 14C. However it should not be sosmall that there may be a risk that frictional forces acting between thefloating seal 21 and the tapered surface 14C will not be overcome by thefluid pressure loading on the clapper 16 should there be a tendency fornormal fluid flow to be reestablished in the direction of arrow B sothat the valve fails to reopen to allow such flow.

In order to operate the valve as a block or shut off valve, the handle20 is moved to its other position and that movement is transmitted tothe clapper 16 through the hinge pin 18, the pegs 18A and the lever 17so that the clapper 16 is seated, and held seated, regardless of inwhich direction fluid might be tending to flow through the through bore12.

Arrangement of the clapper 16 for face to face contact with the crescentshaped abutment surface 15 which extends over the top and down thesides, but not at the bottom, leads to the seating loads being taken bythe valve body 10 without significant risk of debris being trappedbetween the clapper 16 and the seat 14. Such debris will gravitate tothe bottom of the through bore 12 and be pushed through the centralaperture of the annular valve seat 14 by the clapper 16 as it closesrather than be trapped between the clapper and the seat. Provision of atapered valve seat surface 14C which has as small an angle of taper asis practicable facilitates such movement of debris through the centralaperture of the valve seat 14 since the surface of the through bore 12is substantially smooth in the region of the valve seat 14, and thepresence of pockets which could cause accumulation of debris isminimised.

Arrangement of the abutment surface 15 so that it is substantiallynormal to the axis of the through bore 12 avoids any risk that theclapper 16 will jam in its closed position due to any form of wedgeaction between it and the valve seat which has as small an angle oftaper as is practicable. It is not, however, essential that the abutmentsurface be normal to the axis of the through bore 12, it too may betapered relative to the axis of the through bore 12 providing that itsangle of taper is sufficiently large to ensure that the clapper does notjam in face to face contact with it.

Nothing governs the location of clearance between the clapper on the onehand and the surface of the through bore and the tapered surface of thevalve seat on the other if the valve is designed for use in a verticalpipeline. Any convenient arrangement of clapper which cooperates with anabutment surface which extends around at least part of the passagedownstream of the valve seat and provides for access to the annular sealfor reverse fluid flow when the passage is closed such that, onceinitial contact of the seal with the valve seat is established, fluidtight contact between the seal and the valve seat and the clapper isestablished solely by the action of fluid pressure on the seal, would besuitable for such an application.

FIG. 5 shows part of a swinging check valve clapper similar to that ofthe valve shown in FIGS. 1 to 4 but modified to incorporate a differentform of floating metal seal 23 instead of the U-section floating sealring 21. The peripheral portion 23A of the seal 23 is similar to theperipheral portion of the floating seal ring 21 in that it forms ashallow concave radially outer peripheral surface having a greateroutside diameter at its downstream end than at its upstream end. Howeverthat peripheral portion 23A is formed at the radially outer edge of aradially convoluted annular portion 23B which is connected to theperipheral portion 23 A at the upstream end thereof. The radially innerperiphery 23C of the floating seal 23, which is formed at the radiallyinner edge of the convoluted portion 23B, is formed as a thickenedannular rib and is trapped between the profiled clapper portion 16B andan annular retaining plate 24. A concentric ring 23D of low frictionplastics material, such as an elastomer or a polyamide material isprovided at the centre of the concave radially outer peripheral surfaceof the peripheral portion 23A.

The downstream edges of the peripheral portion 23A and of the convolutedportion 23B are in contact with the clapper disc portion 16A (as shownin FIG. 5) up until and when initial contact with the valve seat 14 ismade by the seal 23, there being a clearance between the portions 23Aand 23B and the retaining plate 24. Once the seal 23 has made contactwith the seat 14, the reverse fluid pressure increases the force ofcontact therebetween by forcing the seal 23 further into the taper andup against the retaining plate 24.

The sub-sea check valve shown in FIG. 5 and 7 is similar in manyrespects to the check valve shown in FIGS. 1 to 4. Features of the twovalves which are similar are identified by the same referencecharacters. The following description of the sub-sea check valve shownin FIGS. 6 and 7 is directed towards the features by which that valvediffers from the check valve shown in FIGS. 1 to 4.

Rather than being seated in a shoulder which is formed in the valve body10, the upper portion of the valve seat 14 is fixed to the valve body 10by a stirrup clamp 14D which extends over the valve seat 14 andcooperates with suitable formations in the valve body 10. The downstreamface of the stirrup clamp 14D is normal to the axis of the through bore12 and, together with the exposed portion of the downstream face of thevalve seat 14 serves as the crescent-shaped abutment surface 15 for theclapper disc portion 16A. The hinge pin 18 is fixed in the support 19,there being no handle 20. The support 19 is part of the bonnet 11 ratherthan the body 10. The lever 17 has a lug formed on its face remote fromthe clapper 16. A two-link toggle linkage 25 has one end pinned to thelug and its other end pinned to the lower end of a vertically extendingramrod 26 of a fluid pressure operable actuator 27. The cylinder body 28of the actuator 27 is mounted releasably on the top of the bonnet 11.The ramrod 26 extends in a fluid tight manner through a vertical bore inthe bonnet 11, there being suitable sleeve bearings and seals mounted inthe vertical bore and cooperating with the ramrod 26.

An abutment 31 depends from the bonnet 11 adjacent the downstream end ofthe aperture 13 and serves as a stop for the clapper 16, being spacedfrom the hinge pin 18 sufficiently for the lug and the toggle linkage 25to pass it without touching.

The clapper 16 is formed with a profiled portion 16C which projectsthrough the annular valve seat 14 when the clapper is seated. The end ofthe profiled portion 16C is formed as an arcuate groove 16D which hassubstantially the same radius of curvature as the through bore 12 sothat, when the clapper 16 is in contact with the abutment 31 at theupper end of its range of arcuate movement (as shown in FIG. 7). Thearcuate surface of the groove 16D is a substantial continuation of thewall of the through bore 12.

The interior of the cylinder body 28 is divided into an upper cylinderspace 33 and an annular cylinder space by a piston head 35 at the upperend of the ramrod 26. The annular cylinder space is not shown in FIGS. 6and 7 because of the state of the valve. There is a compression spring36 which reacts on the upper end wall of the cylinder body 28 and urgesthe ramrod 26 downwards.

The actuator 27 is controlled from a remote location, say at thesurface, by a hydraulic control system which is not shown. A torsionspring 37 is anchored relative to the bonner 11 at one end, is passedaround the hinge pin 18 and along the length of the lever 17, and actsto counter balance the weight of the clapper 16.

By buckling, the toggle linkage 25 allows the obturating member,comprising the clapper 15 and the lever 17, to pivot freely relative tothe rest of the structure when the ramrod 26 is held by the action ofthe spring 36 of the actuator 27 in the lower position shown in fulllines in FIGS. 6 and 7, the spring 36 over-coming the effect of fluidpressure in the alcove on the lower end of the ramrod 26. Hence theclapper 16 floats in the fluid and thus is displaced from the annularvalve seat.

In order to clear the through bore 12 for the passage therethrough of apig for any one of the number of possible functional operations to beperformed by such a pig, the actuator 27 is actuated by operation of thecontrol system to connect the annular cylinder space below the pistonhead 35 to a source of hydraulic pressure so that the ramrod 26 isdriven upwards carrying the upper end of the toggle linkage 25 with itto the position shown chain-dotted in FIG. 7, the toggle linkage 5,being extended, acts as a tie to lift the clapper 15 into contact withthe abutment 31 and hold it there. The through bore 12 is then clear forthe pasage of a pig. Only a small amount of fluid pressure is needed inthe annular space 34 as the forces are substantially balanced.

When the obturating member is to be released, say when the operation tobe performed by the pig has been completed, hydraulic fluid pressure isdrained from the annular cylinder space and the piston head 35 andramrod 26 are lowered by expansion of the spring 36. The obturatingmember is thus freed for further normal action.

The fact that the obturating member is suspended from the bonnet 11which is secured releasably to the valve body 10 facilitatesmaintenance. The annular valve seat 14 can be removed and replacedthrough the aperture when the bonnet 11 has been removed. The actuatorcan be removed from the bonnet 11 independently for maintenance.

The check valve can be used to control normal flow in the directionopposite to that indicated by arrow B, but it would be necessary for theclapper is to be held displaced from the valve seat 14 by the actuator27 for such flow to commence. The actuator 27 would be operated to lowerthe ramrod 26 when such flow is to be checked, the flow then causing theclapper 16 to seat automatically.

We claim:
 1. A check valve comprising a housing which forms a throughpassage which is to be connected into a fluid pipeline when the valve isin use, the housing including an annular valve seat which extends aroundthe passage and tapers towards the upstream end of the passage in thecontext of the normal direction of flow through the passage, and anobturating member cooperable with the valve seat to close the throughpassage and displacable from the valve seat to allow fluid flow throughthe through passage, the obturating member carrying an annular sealwhich effects a seal between the obturating member and the valve seatwhen the through passage is closed by the obturating member, wherein theannular seal comprises a floating ring seal, and an abutment surfaceextends around at least part of the passage downstream of the valveseat, the obturating member being adapted to make direct face-to-facecontact with the abutment surface when it closes the through passage andbeing formed to provide for access to the annular seal for reverse fluidflow when the passage is closed by the obturating member, the obturatingmember, abutment surface, valve seat and annular seal being arrangedsuch that the housing reacts a load exerted on it through and by theobturating member without that load being applied to the annular sealsuch that, once initial contact of the seal with the valve seat isestablished, fluid tight contact between the seal and the valve seat andthe obturating member is established solely by the action of fluidpressure on the seal.
 2. A check valve according to claim 1, wherein theobturating member is adapted to make contact with the abutment surfacearound part only of the passage, there being a clearance between theonturating member and wall of the passage whereby said access isprovided.
 3. A check valve according to claim 2 which is to be connectedinto a substantially horizontally extending fluid pipeline when thevalve is in use, wherein the clearance is at the bottom.
 4. A checkvalve according to claim 3, wherein structure of said obturating memberwhich is adapted to contact said abutment surface comprises a discportion which is eccentric to said valve seat when in contact with saidabutment surface so that such contact extends over the top and sides ofthe valve seat but not at the bottom in a plane substantially normal tothe axis of the through passage.
 5. A check valve according to claim 1,wherein the abutment surface is substantially normal to the axis of thethrough passage.
 6. A check valve according to claim 1, wherein thefloating ring seal comprises an annular peripheral portion which forms ashallow concave radially outer peripheral sealing surface having agreater outside diameter at one end than at the other, the peripheralportion being formed at the radially outer edge of a radially convolutedannular portion, the ring seal being carried by the obturating memberwith said one end downstream of the other end, and being downstream froma reaction surface, which is formed in said obturating member, in thecontext of the normal direction of fluid flow through the passage, asthe obturating member approaches the valve seat to close the throughpassage, the concave sealing surface being adapted to engage the taperedvalve seat to effect said seal, the arrangement being such that theperipheral portion is urged into the taper by reverse fluid flow oncethe obturating member has seated and its travel into the taper isresisted by abutment with said reaction surface which in turn is held bythe abutment of the obturating member with the abutment surface.
 7. Acheck valve according to claim 6, wherein the radially inner peripheryof the convoluted annular portion is formed as a thickened rib which isclamped within the obturating member.
 8. A check valve according toclaim 6, wherein a concentric ring of soft sealing material is providedat the centre of the concave radially outer peripheral surface of theouter portion.